Avoiding overruns is one of the major challenges in public software projects. In order to reduce overruns and, in turn, increase the chances of project success, it is essential to have an unbiased overview of the frequency and magnitude of overruns, as well as knowledge about factors which may prevent overruns. In a recent survey of the software industry it was found that the average magnitude of overruns in work-hours was 67% for projects with a public client, compared to 21% for projects with a private client. This paper presents results from two surveys of software companies and professionals that investigate the possible differences between public and private clients, and a review of research on public IT-projects. The results indicate that there are several properties of public projects on the political, organizational and individual level which may contribute to the large overruns. These include artificial deadlines based on political terms, regulations on procurement and development processes, and lack of technology and project management skills. The challenges appear to be common for several countries in the OECD region which have investigated this topic. In order to reduce overruns of public projects, both contractors and government officials have to address these issues.